Method of manufacturing a ball joint

ABSTRACT

A ball joint and a manufacturing method of the same. The ball joint comprises a holder and a ball and rod which is rotatably and movably secured to the holder and a sealing member which is secured between the spherical body of the ball and rod and a sphere receiving portion of the holder. An oil basin to which a cover member is secured from outside of the holder is formed at the bottom portion of the sphere receiving portion of the aforesaid holder, whereby smooth rotation and movement can be obtained.

This is a division of application Ser. No. 492,268 filed Feb. 28, 1990,now U.S. Pat. No. 4,979,844.

FIELD OF THE INVENTION AND RELATED ART

This invention relates to a ball joint and a manufacturing method of thesame, and in particular relates to a ball joint and a manufacturingmethod of the same having an oil basin at the bottom portion of a spherereceiving portion of a holder for the purpose of obtaining smoothrotation or movement.

A conventionally known type of such a ball joint is one comprising aholder having a sphere receiving portion at one end and a connectingportion at the other end, a ball and rod in which one end thereof havinga spherical body which is rotatably and movably positioned in the spherereceiving portion of the aforesaid holder and the other end having aconnecting portion, and a sealing member which is secured to the portionbetween the aforesaid sphere receiving portion and a base portion of theconnecting portion of the ball and rod. Lubricant such as grease issupplied between the above spherical body and the sphere receivingportion. The sealing member also prevents the entrance of dust and soforth into the portion between the spherical body and the spherereceiving portion (for example: Japanese Patent Publication No.26109/1973).

A known method of manufacturing such a ball joint is, for example, thata spherical body is set as a core in a die for a holder. A die castfusible alloy is cast into this die so as to cast the holder in whichthe spherical body is held in a sphere receiving portion. The sphericalbody which is held by this holder and the main body of a rod is weldedin a friction welding manner. A ball and rod in which the spherical bodythereof is held by the holder is thus formed. Then an outer force isapplied between the sphere receiving portion of the aforesaid holder andthe spherical portion of the ball and rod so as to form a space for thepurpose of manufacturing a ball joint (Japanese Patent Publication No.11002/1972) and so forth.

In this method, a spherical body having a smooth surface and highsphericity can be used to form a spherical portion of the ball and rod.Furthermore, the sphere receiving portion of the holder can be cast withthis spherical body used as a core. As a result of this, this method hasan advantage in that a hard chill layer can be formed on the innersurface of the sphere receiving portion.

In the ball joint, described hereinbefore, however, it is required thatthe clearance between the spherical body and the sphere receivingportion is as little as possible. The reason is that a large clearancebetween the spherical body and the sphere receiving portion causes thesphere receiving portion of the holder manufactured by casting to breakif an impacting load is applied thereto. Furthermore, if the lubricantwhich is supplied between the spherical body and the sphere receivingportion has a high viscosity, such as grease, the lubricant enclosed inthe sealing member cannot be sufficiently introduced between thespherical body and sphere receiving portion. As a result, the lubricantcannot be efficiently supplied to the whole portion between thespherical body and the sphere receiving portion, which will cause aseizure or the like during high speed operation and so forth.

In the aforesaid manufacturing method, there is no way to fix thespherical body which is used as a core in the die for casting theholder. The spherical body therefore sometimes moves by the flow of adie-cast fusible alloy when the alloy is cast into the die for castingthe holder. The spherical body sometimes runs out which leaves adefective article. Furthermore, a high degree of skill is required tocast this die-cast fusible alloy, and therefore, this increases thecomplexity of production.

In the conventional manufacturing method, the ball and rod are formed bywelding the spherical body and the main body of the rod in the followingmethod. Two parts are brought into contact each other and they arerelatively rotated under a pressure with the frictional heat at thistime utilized, that is a frictional welding. The pressure applied at thetime of frictional welding to the spherical body and the main body ofthe rod is extremely high. As a result of this high pressure and highfrictional heat which are applied to the spherical body at the time ofthe frictional welding, the sphericity of the spherical bodydeteriorates. After it has become a ball and rod, the sphericity of thespherical body is thus diminished, and the high sphericity of thespherical body which has been produced loses its meaning. Further, it isnecessary to provide a large clearance between the spherical body andthe sphere receiving portion of the holder, so that the clearancecompensates for the difference between the maximum diameter and theminimum. In order to form this large clearance, a large force is neededto be applied to the spherical body and the sphere receiving portion,which leads to unintentional breakage of the sphere receiving portion.Furthermore, in a case in which a plurality of the parts are combined toform a link mechanism, the large clearance between the aforesaidspherical body and the sphere receiving portion integrates, which causesthe accuracy in conducting force and so forth to deteriorate. If thedeterioration in sphericity of the spherical body becomes too large, itcauses a large impacting force to be applied between two parts at thetime of use, and thus causes the sphere receiving portion of the holderto be broken. Furthermore, in the case where the ball and rod are formedby frictional welding, the tempering process after welding must becarried out separately. Furthermore, an extended time between thewelding process and the tempering process causes the welded portion toform a so-called delayed crack. The tempering must be, therefore,applied as soon as possible, and deburring is needed in the weldedportion. As a result of this, the manufacturing process is thusrestricted.

SUMMARY OF THE INVENTION

An object of the present invention, therefore, is to provide a balljoint having an oil basin at the bottom portion of the sphere receivingportion of the holder, and which can smoothly rotate and move.

A further object of the present invention is to provide a ball joint inwhich the spherical portion of the ball and rod has a high sphericity,as a result of which, the clearance between the spherical portion andthe sphere receiving portion of the holder can be decreased. Theshakiness between two parts is thus prevented so as to make the rotationand movement smooth. Furthermore, large impacting loads are preventedfrom occurring between these parts during use.

A still further object of the present invention is to provide a balljoint having an oil basin which is formed by forming an opening at thebottom portion of the sphere receiving portion of the aforesaid holderand securing a cover member to cover the opening. The opening is formedby a sphere supporting portion of the die which is used to fix theaforesaid spherical body at the time of casting the holder with use ofthe spherical body which forms the ball and rod as a core.

A further object of the present invention is to provide a ball jointwherein at the time of casting a holder with the use of the sphericalbody which forms the spherical portion of the ball and rod as a core,the diameter of the spherical body supporting portion of the die whichis used to fix the aforesaid spherical body is designed to besubstantially the same as or larger than the diameter of the main bodyof a rod which forms the connecting portion of the ball and rod. Whenprojection welding the spherical body cast in this holder and the mainbody of the rod which forms the connecting portion of the ball and rod,the opening formed by this spherical body supporting portion at thebottom portion of the sphere receiving portion can be used as anentrance for a supporting electrode.

That is, the present invention provides a ball joint comprising a holderhaving a sphere receiving portion at one end thereof and a connectingportion at the other end, a ball and rod having a spherical portion atone end which is rotatably and movably held in said sphere receivingportion and having a connecting portion at the other end, a sealingmember which is secured between said sphere receiving portion of saidholder and a base portion of said connecting portion of said ball androd, which accommodates a lubricant and acts to prevent the entrance ofdust and so forth, an opening being formed at a bottom portion of saidsphere receiving portion of said holder by a sphere supporting portionof a die for fixing said sphere when casing said holder with a spherewhich forms said spherical portion of said ball and rod as a core, andan oil basin which is formed by positioning a cover member over saidopening to seal the basin from the outside.

This invention provides a method of manufacturing a ball jointcomprising a step of providing a spherical body having high sphericityas a core of a sphere receiving portion into a holder die member, saidspherical body forming a ball and rod by fixing said spherical bodybetween one of a die member and a sphere supporting portion having adiameter substantially same as or larger than the diameter of a mainbody of a rod which forms a connecting portion of said ball and rod,said sphere supporting portion being formed in the other die member, astep of casting a holder in which a spherical body is held in saidsphere receiving portion by casting die-cast fusible alloy into saidholder die member, a step of inserting a supporting electrode from anopening which is formed at the bottom portion of said sphere receivingportion and formed by said sphere receiving portion so as to supportsaid spherical body from lower portion, a step of projection weldingsaid spherical body and a main body of a rod so as to form a ball androd in which a spherical body is held by a holder, a step of applicationof outer force between said sphere receiving portion of said holder andsaid spherical body of said ball and rod for the purpose of forming aspace therebetween, a step of forming an oil basin by fitting a covermember to an opening having a diameter substantially same as or largerthan the diameter of a connecting portion of said ball and rod which isformed by a sphere receiving portion of said die member.

In the ball joint according to the present invention, the holder isformed as that in which the sphere receiving portion thereof has anopening facing substantially at a right angle with respect to theconnecting portion. The connecting portions which are respectivelyprovided for the aforesaid holder side and the ball rod side may be themeans such as outer threads or inner threads to connect with othermembers, where both the same means as one another or different means maybe employed.

The diameter of the opening which is formed in the bottom portion of thesphere receiving portion of the holder preferably is substantially sameas or larger than the diameter of the connecting portion of the ball androd. The opening can be thus used as an entrance of a supportingelectrode which supports the aforesaid spherical body at the time ofjoining by projection welding the spherical body casted in the holderand the main body of the rod which forms the connecting portion of theball and rod.

Furthermore, thanks to manufacturing the ball and rod by projectionwelding the main body of the rod and the spherical body, the sphericityof the spherical body can be increased. That is, when projection weldingthe spherical body and the main body of the rod, the diameter of theopening which is formed by the spherical body supporting portion in thedie is substantially same as or larger than the diameter of the mainbody of the rod, the diameter of the supporting electrode which supportsthe spherical body by being inserted into the opening and which becomesone side electrode at the time of projection welding can besubstantially same as or larger than the diameter of the aforesaid mainbody of the rod. As a result of this, electric current can beconcentrated into the portion between the spherical body and the mainbody of the rod at the time of projection welding, the welding in thisportion can be performed efficiently. And simultaneously, the portion ofthe spherical body in contact with the supporting portion of thesupporting electrode can keep its surface smoothness and sphericity andso forth.

The means for fixing a cover member which forms an oil basin which isformed in the bottom portion of the sphere receiving portion of theholder may be that an annular projection is formed in the circumferenceof the edge of the opening to which this cover member is fixed for thepurpose of caulking the annular projection.

Furthermore, the method of manufacturing a ball joint equipped with aball and rod having high sphericity at the sphere portion thereof willnow be described. A spherical body having high sphericity is used inprinciple, then this spherical body and the main body of the rod may beprojection welded. The method of this welding may be a laminatedprojection welding and so forth, and preferably would be a buttprojection welding. The employment of the projection welding candecrease weld burrs, the deburring process of cutting the burrs and soforth is therefore needless. Furthermore, tempering of the weldingportion can be easily performed by passing electric current again in thestate after projection welding the spherical body and the main body ofthe rod. As a result of this, so-called delayed cracks which occur inthe welded portion of, for example, in hard carbon steel by leaving fora long time after welding can be completely prevented by carrying outtempering continued after the welding.

Since the ball joint according to the present invention has an oil basinin the bottom portion of the sphere receiving portion of the holder,from which lubricant such as grease is supplied from both the upper andlower portions of the portion between the spherical body of the ball androd and the sphere receiving portion of the holder, the lubricant can bered smoothly. The lubricant can be thus efficiently supplied to theportion between this spherical body and the sphere receiving portion.Thanks to this efficient supply of the lubricant, smooth rotation andmovement can be achieved even at high speed operation and so forthwithout problems such as seizing and so forth.

Furthermore, according to the present invention, the spherical body usedas a core is fixed by one of the die members and the spherical bodysupporting portion which is provided on the other die member, thespherical body can be prevented from runout by cast die-cast fusiblealloy, thanks to which, defects can be prevented from being generated.Since the spherical body and the main body of the rod is joined by theprojection welding, a ball and rod with the use of a spherical bodydisplaying a high sphericity can be manufactured without anydeterioration in its sphericity. Furthermore, the sphere receivingportion of the holder is casted with the use of this spherical bodyhaving high sphericity as a core, the clearance between this spherereceiving portion and the spherical body can be arranged as minimum aspossible to meet requirements. As a result of which a large impactingforce can be thus prevented during usage, and a ball joint displayinglarge durability can be thus manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view illustrating a ball joint of anembodiment of the present invention;

FIG. 2 is a left side view of FIG. 1;

FIG. 3 is a right side view of FIG. 1;

FIG. 4 illustrates a method of manufacturing a holder with a sphericalbody used as a core;

FIG. 5 is a partial cross sectional view illustrating the holder inwhich a spherical body is cast;

FIG. 6 is a right side view of FIG. 5;

FIG. 7 is a plan view of FIG. 5;

FIG. 8 illustrates a method of joining a spherical body which is cast ina holder and a main body of a rod by projection welding; and

FIG. 9 is a cross sectional view illustrating a ball and rod and aholder which are formed by projection welding shown in FIG. 8.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to the accompanying drawings, an embodiment of a ball jointaccording to the present invention will now be described.

FIGS. 1 to 3 illustrate a ball joint of one embodiment of the presentinvention. This ball joint comprises a holder 1 having a sphericalreceiving portion 2 at one end thereof and a connecting portion 3 at theother end thereof. It further comprises a ball and rod 4 at one endthereof having a spherical receiving portion 2 at one end thereof and aconnecting portion 3 at the other end thereof. It further comprises aball and rod 4 at one end thereof having a spherical portion 5 which hashigh sphericity and which is rotatably and movably secured with minimumnecessary clearance in the spherical receiving portion 2 of theaforesaid holder 1. The ball and rod 4 comprise a connecting portion 6at the other end thereof. The ball joint further comprises a sealingmember 7 which is located between the aforesaid spherical portion 2 anda base portion of the connecting portion 6 of the ball and rod 4. Thesealing member 7 serves to accommodate lubricant such as grease which issupplied between the aforesaid spherical portion 5 and the sphericalreceiving portion 2. And it also serves to prevent entrance of dust andso forth into the portion between this spherical portion 5 and thespherical receiving portion 2. The aforesaid holder 1 is formed in sucha manner that the spherical receiving portion 2 has an opening arrangedsubstantially at a right angle with respect to the connecting portionthereof. An oil basin portion 9 which is closely sealed by a covermaterial 8 is formed at the bottom portion of spherical receivingportion 2 of the holder 1.

The cover material 8 which forms the aforesaid oil basin 9 employed inthis embodiment is composed of a thin disc plate. It is fixed bycaulking an annular projection 10 which is provided around thecircumference of an opening which serves as the oil basin 9 by casingthe holder 1, the opening being formed at the bottom portion of thespherical receiving portion 2. The connecting portion 3 of the aforesaidholder 1 is formed in the shape of internal threads 3a. The connectingportion 6 of the ball and rod 4 is formed in the shape of outer threads6a. A hexagonal tool securing portion 11 which serves to be secured by atool for rotating the ball and rod 4 at the time of securing the outerthreads 6a to the other member is formed in the base portion of the balland rod 4. A tool securing portion 12 in a substantially rectangularshape to which a tool is secured is also formed at one end of theconnecting portion 3 of the holder 1. Furthermore, one end portion 7a ofthe aforesaid sealing member 7 is secured to the aforementioned toolsecuring portion 11. The other end 7b is secured to the edge of theopening of the spherical receiving portion 2, a lubricant pocket 13 thusbeing formed therebetween. An edge surface 14 is formed in the edgeportion of the opening of the spherical receiving portion 2 of theaforesaid holder 1 for the purpose of regulating a moving angle of theball and rod 4 which is secured by this spherical receiving portion 2.

The manufacturing method of the ball joint according to the presentinvention will now be described.

The holder 1 is cast with a spherical body 4a as a core. The sphericalbody 4a which is accommodated in the cast holder 1 and the main body 4bof the rod is projection welded so as to manufacture a ball and rod 4.

That is, as shown in FIG. 4, the spherical body 4a having highsphericity is set as a core of the spherical receiving portion 2 in aholder casing die 20 which is vertically divided. Next, the sphericalbody 4a which is used as a core is inserted between an upper die member21 and a sphere receiving portion 23 which is provided on lower diemember 22 and the diameter of which is larger than that of the lowerportion of the main body 4b of the rod which forms a connecting portion6 of the ball and rod 4 for the purpose of fixing. A core 24 for formingthe inner threads 3a is set at the portion which forms the connectingportion 3 of the holder 1. Then, a die-cast fusible alloy is cast intothe holder casting die 20 so as to cast the holder 1. In the cast holder1, as shown in FIGS. 5 to 7, the spherical body 4a which becomesspherical portion 5 of the ball and rod 4 is cast and held in thespherical receiving portion 2 of the holder 1. An opening 9a whichbecomes an oil basin 9 is formed in the bottom portion of the aforesaidspherical receiving portion 2. An annular projection 10 which is caulkedat the time of fixing the cover material 8 is formed in thecircumference of the edge of the opening. In this embodiment, the innerthreads 3a and the tool securing portion 12 are formed, in this state,in the connecting portion 3 of the holder 1. After casting the holder 1in which the spherical body 4a is cast, as shown in FIG. 8, a supportingelectrode 25 for projection welding is inserted through the opening 9awhich is formed by the sphere receiving portion 23 of the lower diemember 22 in the bottom portion of the holder 1 at the time of castingthe holder 1 so as to support the spherical body 4a. The spherical body4a and the main body 4b of the rod are abutted against with each otherat their ends. Under a predetermined pressure F a predetermined electriccurrent is passed for a predetermined weld time for the purpose ofprojection welding these ends. The electric current is again passedthrough main body 4b and spherical body 4a for the purpose of tempering.The holder 1 in which a spherical body 5 of the ball and rod 4 cast inthe spherical receiving portion 2 is thus formed. Usage of the aforesaidsupporting electrode 25 in which diameter d2 of its supporting portion25a is larger with respect to the diameter d1 of the aforesaid main body4b of the rod, and smaller with respect to the diameter d3 of theopening 9a, as a result of which, it does not contact thecircumferential surface of the opening a 9a (that is, the relationshipis: d1<d2<d3) for efficient projection welding between the sphericalbody 4a and the main body 4b of the rod. Furthermore, the spherical body4a and the main body 4b of the rod can be welded without anydeterioration in smoothness and sphericity of the spherical body 4a towhich .the supporting electrode 25 is in contact. In order for thespherical portion 5 of the ball and rod 4 to be able to rotate and morewith respect to the spherical receiving portion 2 of the holder 1, asmall space is formed between the sphere receiving portion 2 of theholder 1 which has been thus formed and the spherical portion 5 of theball and rod 4 by applying an outside force by, for example, applying asmall impact by patting the outer circumference of the aforesaid spherereceiving portion 2, or applying a tension to the ball and rod 4. Thenthe opening 9a which is formed at the bottom portion of the spherereceiving portion 2 of the holder 1 is filled with the lubricant such asgrease and so forth. The cover member 8 is then fitted into the edge ofthis opening 9a and the annular projection 10 which is formed in thecircumference of this opening 9a is caulked so as to form the oil basin9 with this cover member 8 fixed to the edge of the opening 9a.

Furthermore, as shown in FIG. 1, the sealing member 7 is secured to theportion between the edge of the opening in the sphere receiving portion2 of the holder 1 and the tool securing portion 11 which is formed atbase portion of the connecting portion 6 of the ball and rod 4. Then thelubricant pocket 13 which is formed by this sealing member 7 is filledwith the lubricant such as grease and so forth.

What is claimed is:
 1. A method of manufacturing a ball joint comprisingthe steps of:providing a spherical body having high sphericity,providing a cylindrical rod, providing a socket die comprising first andsecond die members, said second die member including a sphere supportingportion having a diameter substantially the same as or larger than thediameter of said rod and a cup shaped end which conforms to the shape ofsaid spherical body, setting said spherical body in said cup shaped endof sphere supporting portion of said second die member, assembling saidfirst and second die members such that said spherical body is fixedbetween said sphere supporting portion of said second die member and asphere holding portion of said first die member, casting a die castfusible alloy into said socket die, allowing said alloy to harden insaid socket die, thereby forming a socket about said spherical body,removing said formed socket from said socket die by separating saidfirst and second die members, thereby forming a cylindrical opening in abottom portion of said formed socket in the area vacated by said spheresupporting portion of said second die member, said opening having adiameter substantially the same as or larger than the diameter of saidrod, inserting a supporting electrode through said opening to supportsaid spherical body at a lower portion thereof, placing said rodopposite said opening and on top of said spherical body, such that saidrod is in axial alignment with said opening and in contact with saidspherical body, projection welding said spherical body to said rod byapplying a predetermined axial force, in the direction of said sphericalbody, to said rod and passing a predetermined electric current throughsaid electrode, thereby forming a ball and rod in which said sphericalbody is held by said socket, removing said supporting electrode,applying a pulling force between said socket and said spherical body ofsaid ball and rod to from a space therebetween, and fitting a covermember to said opening, said cover member having a diametersubstantially the same as said opening, thereby forming an oil basin insaid bottom portion of said socket.